Abstract 2598: RHAMM- A potential predictor of metastasis and therapeutic target in kidney cancer

Abstract

Abstract Up to 25% of patients with renal cell carcinoma (RCC) have metastasis at initial diagnosis. Current targeted therapies (e.g., Sorafenib) are not curative and the 5-year survival of these patients is <10%. Molecular determinants of RCC growth and metastasis may be accurate prognostic markers for metastasis and could be targeted for therapy. We evaluated the expression of 5 genes (and their splice variants) as prognostic indicators. We also tested the therapeutic efficacy of the combination of 4-methylumbelliferone (4-MU), a non-toxic, orally bioavailable hyaluronic acid (HA) synthesis inhibitor and Sorafenib (Soraf). Tumor specimens were collected from RCC patients undergoing nephrectomy (n=81; T1, 40; T2+, 41; Grade 1, 5; Grade 2, 32; Grade 3, 25; Grade 4, 19). Nine patients developed metastasis within 24 months. Tissue-RNA was subjected to Q-PCR for HA receptors (CD44, RHAMM), chemokine receptors (CXCR4, CXCR7); and chemokines (SDF1-α,β,γ). mRNA levels were correlated with metastasis by logistic regression. Effect of 4-MU, Soraf and 4-MU+Soraf on cell proliferation, cell cycle and apoptosis was examined in RCC cells (HTB46, 786-O, ACHN, 769-P, A498) by cell counting, flow cytometry and Cell Death ELISA. Boyden chamber was used for motility assay. Effect on cell cycle, apoptosis, and HA receptor levels were evaluated by immunoblotting and Q-PCR. RHAMM expression (157±124) was 8-fold elevated in tumors which later metastasized when compared to those which did not (20.1±31.5; P=0.005). In univariate analysis age, grade, stage and RHAMM levels significantly correlated with metastasis. In multivariate analysis, only RHAMM significantly correlated with metastasis (P=0.03; chi-sq = 4.6; sensitivity 88.9%; specificity 90%). Combination of 4-MU (0.2 mM) and Soraf (2.5 or 5 μM), at non-cytotoxic doses caused 60-90% inhibition in proliferation after 48-72 h treatment and motility in RCC cells. Inhibition of cell proliferation could not be reversed by HA addition. Only the combination induced cycle arrest in late S- and G2-M phases (1.5-2.5-fold) and induced apoptosis (3-4-fold). Cell cycle arrest and apoptosis were confirmed by increased phospho-Chk1 and PARP levels. 4-MU+Soraf combination down regulated CD44 and RHAMM mRNA levels by 2- and 68-fold, respectively. RHAMM expression in RCC tissues is potentially an independent prognostic indicator for metastasis. 4-MU+Soraf combination which targets RHAMM expression inhibits RCC cell growth and motility. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2598. doi:10.1158/1538-7445.AM2011-2598